16 



A TEXTBOOK OF BOTANY 



[On. Ill, 1 



\jeature do foliage leaves vary little and that is the 



[S| nf their green jissue, whicjiJs--Ja3aa4y 



ig same no matter what their sizes and 

 The thin fiat expanse ot green tissue, called the 

 is always the essential, and often the only, part of the leaf. 

 In many kinds, however, the blade is provided with a slender, 

 cylindrical stalk, called the PETIOLE, various in length even 



up~lo several feet ; and upon it thelj 

 blade is adjusted to the light, and I 

 has free play in the wind. In addi- 1 

 tion, some kinds possess a pair o^j 

 small appendages, one on each side 

 of the base of the petiole, called 

 STIPULES, which, though usually 

 green like the blade, are very diverse 

 in form. Blade, petiole, and stipulesjj 

 are parts of a complete leaf, of which! 1 

 a typical example is pictured hefe-M 

 with (Fig. 1). 



In some kinds of leaves, es- 

 pecially large ones, the blade is 

 not all one piece, but is cleft more 

 the or less into divisions, as familiar in 

 Quince, showing blade, petiole, Oak or Maple. The same process 

 and stipules; reduced (After cont inued much farther results in 



Gray s Structural Botany.) 



the formation of separate LEAFLETS, 



each with a stalk of its own, as in Rose or Strawberry 

 (Fig. 37), while the leaflets also may become themselves 

 subdivided, even more than once, as in some kinds of Ferns. 

 Such leaves are called .COMPOUND , in distinction from^siMPLE, 

 the two being distinguishable by the fact that the leaflets 

 of a compound leaf always stand in one flat plane, while 

 sample leaves are distributed around a stem, at least at their 

 bases. Further, leaflets have n^ fajHs in f.hpir axils, but 



FIG. 1. A leaf 



whether simple Qnxmnpound, always do. 

 hile typical leaves, the kinds designate^ foliage, are 



